| 11. |
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| 12. |
- Ghazi Moradi, Farnaz, et al.
(författare)
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Spectroscopy of the neutron-deficient N=50 nucleus Rh-95
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89:4, s. 044310-
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Tidskriftsartikel (refereegranskat)abstract
- The neutron-deficient semimagic (neutron number N = 50) Rh-95 nucleus has been produced at high spins using the projectile-target system Ca-40 + Ni-58 at 125 MeV beam energy. The gamma-decays of levels populated by the 3p fusion evaporation reaction channel were studied using gamma-gamma coincidences, and 20 new gamma-ray transitions involving 15 new positive-and negative-parity states were observed. Spin and parity for many of the excited states were firmly deduced for the first time using the combined directional angular correlation and direction-polarization techniques. The observed structures are discussed within the framework of large-scale shell model calculations. E1 transition strengths were deduced and used together with the results of the shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.
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| 13. |
- Jiang, Hui, et al.
(författare)
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Magnetic moments of low-lying states in tin isotopes within the nucleon-pair approximation
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89:1, s. 014320-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic moments of the first excited 2(+) state in even-even nuclei Sn102-130 and the low-lying yrast states in odd-mass nuclei Sn-101-109,Sn-123-131 are calculated within the framework of the nucleon-pair approximation (NPA) of the shell model, by using the standard multipole-multipole interaction. Our calculations agree reasonably well with available experimental data. The g(2(1)(+)) values, as well as the contributions from their spin and orbital angular momentum components, are evaluated in terms of the small NPA subspace spanned by S and D nucleon pairs. The magnetic moment is suggested to be a sensitive probe of the nuclear wave function in this region.
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| 14. |
- Jiang, Hui, et al.
(författare)
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Nucleon pair approximation description of the low-lying structure of Te-108,Te-109 and I-109
- 2013
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:4, s. 044332-
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Tidskriftsartikel (refereegranskat)abstract
- The low-lying level schemes and electromagnetic transitions of Te-109, I-109, and the neighboring even-even nucleus Te-108 are calculated within the framework of the SD-pair approximation of the nuclear shell model. Good agreement is obtained between the calculated results and experimental data. The favored components of low-lying bands are discussed in the collective nucleon-pair subspace. The weak-coupling picture shown in these nuclei and its relationship with residual quadrupole-quadrupole interaction between valence protons and neutrons are analyzed.
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| 15. |
- Liotta, Roberto J.
(författare)
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Aurel sandulescu - A life dedicated to nuclear physics
- 2013
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 413:1
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Tidskriftsartikel (refereegranskat)abstract
- I was surprised to receive an invitation letter from Andrei Dorobantu, whom I did not know, to give a talk about pairing excitations at the Predeal International School of 1978, which I accepted. This was the first time that I would visit Romania, and I knew very little about the research that was performed in the country.In my talk I was showing the role of the pairing mode in a rather popular theory at that time which was called Nuclear Field Theory. Suddenly I was interrupted in a rather brusque fashion by a man with an acute and loud voice, telling me that it has been shown by somebody that the Nuclear Field Theory does not converge. I was very upset by this interruption, particularly because he was right. I told him this and asked him to wait up at the end of my talk. During the coffee break the man came to me and presented himself. It was the first time I came into contact with the extraordinary person that is Aurel Sandulescu.During the coffee break we spoke about his research, especially in alpha decay. I was interested in this subject because just then I had started to perform calculations in relation to experiments carried out at my Institution in Stockholm, which at that time was called the Research Institute of Physics.We continued with our discussions during the whole duration of the School, often with his wife, Violeta, present. I became amazed by the extensive work he had done since the late 1950s on microscopic treatments of alpha decay. He had studied the decay of both normal and superfluid as well as spherical and deformed nuclei, all within the framework of the shell model or its BCS equivalent. I was very enthusiastic about this, since I was convinced that one should, in principle, be able to describe the decay process by using a shell model representation. I was disappointed to realize that he did not agree with me. I insisted that from a purely theoretical point of view the shell model was, rather more than a model, an excellent representation to describe nuclear processes. However, with the perspective that the passing years provides, I have since had to admit that one needs cluster components in the shell model wave functions in order to properly describe the clustering and subsequent decay. For Aurel, this realization led him to consider the decay as a fission process. It was through this that he found, just by simply looking through the penetrability, that cluster radioactivity is a valid form of decay, as was indeed confirmed experimentally several years afterwards. This new form of radioactive decay has had a profound influence on nuclear physics. It opened the way to the investigation of the structure and exotic forms that superheavy nuclei may acquire, since one expects that heavy clusters are likely to be emitted from these nuclei. The importance of cluster decay, and the theory behind its discovery, is of great relevance even today. This can be attested, for example, by the recent prediction of Poenaru, Gherghescu and Greiner (2011 Phys. Rev. Lett 107 062503) that in some superheavy nuclei this form of decay is dominant even over alpha emission, thus making cluster decay a powerful tool in the detection of superheavy nuclei.The description of cluster decay as a fragmentation process and its relation to heavy and superheavy elements was a natural extension of the research that Aurel Sandulescu was conducting at that time. Just before the cluster decay paper appeared he addressed the important question of the production of superheavy elements. The straightforward method of reaching this is by heavy ions collisions, but the question was: which nuclei should one use as reaction partners? Sandulescu proposed choosing those nuclei that provide a minimum of the potential energy, which was an important step in the synthesis of superheavy nuclei.Another subject which is of great importance in nuclear physics and in which Sandulescu played a crucial role was his prediction of neutronless spontaneous binary and ternary fission. He was so elated and eager about this that he even contributed to the experimental discovery of this rare phenomenon. Since then, there have been many theoretical as well as experimental studies performed in this and similar subjects related to cold fission processes. Particularly relevant in the framework of this conference are his studies on the damping of collective modes in deep inelastic collisions. He treated this difficult subject by extending a formalism derived for open systems to nuclear collective motions. The master equation that he thus obtained describes well the dynamics of degrees of freedom not only in the damping of excited nuclear states, but also particularly in heavy ion collisions and in the decaying of the most collective states in nuclear physics—giant resonances.He has also analyzed the complicated mechanisms that induce the clustering of nucleons, which led to his realization that the cluster structure can be viewed as solitons moving on the nuclear surface.This intense scientific work was followed by other related activities. In Romania he became a full professor in 1970, a corresponding member of the Romanian Academy of Sciences in 1991, an ordinary member in 1992 and Vice President in the period 1994–1998. Most remarkable is that he tried to influence the development of Science in the country by himself becoming a politician. Thus, he was a member of the Romanian Parliament in the period 1996–2000. Outside of Romania he has also undertaken remarkable activities. He has been Invited Scientist and Invited Professor to many institutions around the world. One should mention in particular his position as Vice Director of the Joint Institute of Nuclear Research, Dubna, Russia, in the period 1983–1986. He has proceeded through all these endeavors by attracting many foreign scientists to Romania, including myself. But especially important was his influence upon students, many of whom are today recognized physicists and leaders of Romanian physics.It is in recognition of his contribution to physics, especially nuclear physics, as well as his work for Romanian science that this School is organized in his honour, on the occasion of his 80th birthday.I cannot finish this short account without mentioning the person that accompanied Aurel Sandulescu through all his life, his wife of more than fifty years, Violeta. She also was an exceptional person. In her youth she was a very dedicated sporty girl, very athletic, very courageous, very fair and, above all, very generous. These qualities remained with her throughout her life. With deep sorrow I learnt that she passed away three months ago, still youthful and enthusiastic.
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| 16. |
- Liotta, Roberto J.
(författare)
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Developments in radioactive decay during the last Century
- 2013
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 413:1, s. 012012-
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Tidskriftsartikel (refereegranskat)abstract
- In this talk a review of the developments in radioactive decay processes that have taken place during the last Century, and the great outgrowths of these developments in Modern Physics, is presented.
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| 17. |
- Liotta, Roberto
(författare)
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MULTISTEP SHELL MODEL METHOD IN THE COMPLEX ENERGY PLANE
- 2010
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Ingår i: NUCLEAR STRUCTURE IN CHINA 2010. - : WORLD SCIENTIFIC PUBL CO PTE LTD. ; , s. 88-95
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Konferensbidrag (refereegranskat)abstract
- We have adopted the multistep shell model in the complex energy plane to study excitations occurring in the continuum part of the nuclear spectrum. In this method of solving the shell model equations one proceeds in several steps. In each step one constructs building blocks to be used in future steps. We applied this formalism to analyze the unbound nucleus Li-12. In this case the excitations correspond to the motion of three particles partitioned as the product of a one-particle and two-particle systems.
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| 18. |
- Procter, M. G., et al.
(författare)
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Anomalous transition strength in the proton-unbound nucleus (109)(53)I56
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:3, s. 118-122
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Tidskriftsartikel (refereegranskat)abstract
- A lifetime measurement has been made for the first excited 11/2(+) state in the proton-unbound nucleus (109)(53)I56 using the recoil-distance Doppler-shift method in conjunction with recoil-proton tagging. The experimental reduced transition probability is considerably smaller than the prediction of theoretical shell-model calculations using the CD-Bonn nucleon-nucleon potential. The discrepancy between the theoretical and experimental reduced transition strengths in this work most likely arises from the inability of the current shell-model calculations to accurately account for the behavior of the unbound nuclear states.
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| 19. |
- Procter, M. G., et al.
(författare)
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Isomer-tagged differential-plunger measurements in Xe-113(54)
- 2013
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:1, s. 014308-
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Tidskriftsartikel (refereegranskat)abstract
- The 278-keV M2 gamma decay from the vh(11/2) isomeric state in Xe-113 has been observed for the first time using the recoil-isomer tagging technique. The half-life of the isomer has been measured to be 6.9(3) mu s. The derived B(M2) value is in agreement with the trend of systematic measurements of M2 transition strengths in neutron-deficient tellurium and tin isotopes. The lifetime of the first excited state in the vh(11/2) band has been measured using the recoil distance Doppler-shift method. The extracted B(E2) value has been compared to theoretical CD-Bonn calculations and recent lifetime measurements in Te-109. This comparison of B(E2) values has been used to shed light on the possible influence of collective degrees of freedom on M2 transition strengths in the most neutron-deficient xenon nuclei. The vh(11/2) band is deduced to have a degree of deformation comparable with the ground-state bands of the even-mass xenon isotopes. However, the value deduced in this work indicates a loss of collective behavior when compared with the lower-mass Te-109. This result suggests that, while changes in deformation may be partly responsible for the observed trend in B(M2) values for increasing Z, other effects may also be present.
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| 20. |
- Qi, Chong, et al.
(författare)
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Abrupt changes in alpha-decay systematics as a manifestation of collective nuclear modes
- 2010
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 81:6, s. 064319-
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Tidskriftsartikel (refereegranskat)abstract
- An abrupt change in alpha-decay systematics around the N = 126 neutron shell closure is discussed. It is explained as a sudden hindrance of the clustering of the nucleons that eventually form the a particle. This is because the clustering induced by the pairing mode acting upon the four nucleons is inhibited if the configuration space does not allow a proper manifestation of the pairing collectivity.
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